Energetics of charge transfer in collisions of rare-gas ions with H 2, D 2, O 2, N 2 and no molecules

Abstract

Investigations of simple charge transfer in collisions of Ne +, Ar + and Kr + ions with H 2, D 2, O 2, N 2 and NO molecules have been performed in ion beam-gas target experiments at incident ion energies in the range 30–373 eV, using a variable-angle tandem mass spectrometer. Distributions in kinetic energy E 3 of the product ions were measured at the observation angle O = 90 ° with respect to the incident ion direction. These E 3-spectra give information concerning the internal energy changes Q of the various transfer reactions, and the internal states of the product ions. Pronounced peaks in the E 3-spectra when E 3 ≅ 0 were observed in all cases. These peaks correspond to thermo-neutral or slightly exothermic reaction channels, in which little momentum is exchanged between collision partners, and which have Q-values in the range 0 ≦ Q ≦ 0.3 eV. In addition, energetic product ions (0.5 ≦ E 3 ≦ 4.0 eV) were observed, indicating that transfer also takes place via either strongly exothermic channels, slightly endothermic channels, or both. Dissociative charge transfer reactions in Ne + − O 2, Ar + − D 2, and Ar + − H 2 collisions have been studied as well, and the results and interpretations of these experiments are also presented.